/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect;
import static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
import static com.google.common.collect.ImmutableMapEntry.createEntryArray;
import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ImmutableMapEntry.TerminalEntry;
import javax.annotation.Nullable;
/**
* Implementation of {@link ImmutableMap} with two or more entries.
*
* @author Jesse Wilson
* @author Kevin Bourrillion
* @author Gregory Kick
*/
@GwtCompatible(serializable = true, emulated = true)
final class RegularImmutableMap<K, V> extends ImmutableMap<K, V> {
// entries in insertion order
private final transient ImmutableMapEntry<K, V>[] entries;
// array of linked lists of entries
private final transient ImmutableMapEntry<K, V>[] table;
// 'and' with an int to get a table index
private final transient int mask;
RegularImmutableMap(TerminalEntry<?, ?>... theEntries) {
this(theEntries.length, theEntries);
}
/**
* Constructor for RegularImmutableMap that takes as input an array of {@code TerminalEntry}
* entries. Assumes that these entries have already been checked for null.
*
* <p>This allows reuse of the entry objects from the array in the actual implementation.
*/
RegularImmutableMap(int size, TerminalEntry<?, ?>[] theEntries) {
entries = createEntryArray(size);
int tableSize = Hashing.closedTableSize(size, MAX_LOAD_FACTOR);
table = createEntryArray(tableSize);
mask = tableSize - 1;
for (int entryIndex = 0; entryIndex < size; entryIndex++) {
@SuppressWarnings("unchecked")
TerminalEntry<K, V> entry = (TerminalEntry<K, V>) theEntries[entryIndex];
K key = entry.getKey();
int tableIndex = Hashing.smear(key.hashCode()) & mask;
@Nullable ImmutableMapEntry<K, V> existing = table[tableIndex];
// prepend, not append, so the entries can be immutable
ImmutableMapEntry<K, V> newEntry = (existing == null)
? entry
: new NonTerminalMapEntry<K, V>(entry, existing);
table[tableIndex] = newEntry;
entries[entryIndex] = newEntry;
checkNoConflictInKeyBucket(key, newEntry, existing);
}
}
/**
* Constructor for RegularImmutableMap that makes no assumptions about the input entries.
*/
RegularImmutableMap(Entry<?, ?>[] theEntries) {
int size = theEntries.length;
entries = createEntryArray(size);
int tableSize = Hashing.closedTableSize(size, MAX_LOAD_FACTOR);
table = createEntryArray(tableSize);
mask = tableSize - 1;
for (int entryIndex = 0; entryIndex < size; entryIndex++) {
@SuppressWarnings("unchecked") // all our callers carefully put in only Entry<K, V>s
Entry<K, V> entry = (Entry<K, V>) theEntries[entryIndex];
K key = entry.getKey();
V value = entry.getValue();
checkEntryNotNull(key, value);
int tableIndex = Hashing.smear(key.hashCode()) & mask;
@Nullable ImmutableMapEntry<K, V> existing = table[tableIndex];
// prepend, not append, so the entries can be immutable
ImmutableMapEntry<K, V> newEntry = (existing == null)
? new TerminalEntry<K, V>(key, value)
: new NonTerminalMapEntry<K, V>(key, value, existing);
table[tableIndex] = newEntry;
entries[entryIndex] = newEntry;
checkNoConflictInKeyBucket(key, newEntry, existing);
}
}
static void checkNoConflictInKeyBucket(
Object key, Entry<?, ?> entry, @Nullable ImmutableMapEntry<?, ?> keyBucketHead) {
for (; keyBucketHead != null; keyBucketHead = keyBucketHead.getNextInKeyBucket()) {
checkNoConflict(!key.equals(keyBucketHead.getKey()), "key", entry, keyBucketHead);
}
}
private static final class NonTerminalMapEntry<K, V> extends ImmutableMapEntry<K, V> {
private final ImmutableMapEntry<K, V> nextInKeyBucket;
NonTerminalMapEntry(K key, V value, ImmutableMapEntry<K, V> nextInKeyBucket) {
super(key, value);
this.nextInKeyBucket = nextInKeyBucket;
}
NonTerminalMapEntry(ImmutableMapEntry<K, V> contents, ImmutableMapEntry<K, V> nextInKeyBucket) {
super(contents);
this.nextInKeyBucket = nextInKeyBucket;
}
@Override
ImmutableMapEntry<K, V> getNextInKeyBucket() {
return nextInKeyBucket;
}
@Override
@Nullable
ImmutableMapEntry<K, V> getNextInValueBucket() {
return null;
}
}
/**
* Closed addressing tends to perform well even with high load factors.
* Being conservative here ensures that the table is still likely to be
* relatively sparse (hence it misses fast) while saving space.
*/
private static final double MAX_LOAD_FACTOR = 1.2;
@Override public V get(@Nullable Object key) {
return get(key, table, mask);
}
@Nullable
static <V> V get(@Nullable Object key, ImmutableMapEntry<?, V>[] keyTable, int mask) {
if (key == null) {
return null;
}
int index = Hashing.smear(key.hashCode()) & mask;
for (ImmutableMapEntry<?, V> entry = keyTable[index];
entry != null;
entry = entry.getNextInKeyBucket()) {
Object candidateKey = entry.getKey();
/*
* Assume that equals uses the == optimization when appropriate, and that
* it would check hash codes as an optimization when appropriate. If we
* did these things, it would just make things worse for the most
* performance-conscious users.
*/
if (key.equals(candidateKey)) {
return entry.getValue();
}
}
return null;
}
@Override
public int size() {
return entries.length;
}
@Override boolean isPartialView() {
return false;
}
@Override
ImmutableSet<Entry<K, V>> createEntrySet() {
return new ImmutableMapEntrySet.RegularEntrySet<K, V>(this, entries);
}
// This class is never actually serialized directly, but we have to make the
// warning go away (and suppressing would suppress for all nested classes too)
private static final long serialVersionUID = 0;
}